The precise detection of the rotational rotor position of the motor rotor is important for a secure and energy-efficient operation of an automotive auxiliary device, which is driven by an electronically commutated drive motor, since only in this way can an exact control and regulation of the drive motor be realized. The precise detection helps to avoid undesired operations, such as start-up problems, for example, so-called toggling, or other operational problems which can in particular occur with positive displacement pumps due to greatly varying torques. The precise detection also facilitates an accurate timing of the commutation in the stator coils so that the absolute energy consumption can be minimized.
Against this background, hall-sensors are commonly used to provide an accurate rotor position detection. The hall-sensors can be arranged axially or radially to the motor rotor which is magnetically excited by permanent magnets. The hall-sensors thereby detect rotating magnetic fields of the motor rotor generated by the permanent magnets and their magnetic poles, respectively.
The absolute field strength of the magnetic field and the size of interfering signals are crucial for the accuracy of the rotor position detection by hall-sensors.